Composite materials such as circuit boards having additional layers in the shape of metallisations, which are arranged on a ceramic base material, are known in the state of the art in the most various types and are used for purposes in the field of power electronics. Moreover, and as an example, the active soldering method designed to fasten the additional layer on the base material is known from DE 22 13 115. In this method which is specifically also used for producing a metal ceramic substrate, a force-fit connection between a metal foil, for example a copper foil, and a ceramic substrate, for example an aluminium nitride ceramic, by using an appropriate solder material at a temperature from 650 to 1,000° C. In addition to a main component, such as copper, silver and/or gold, the solder material also contains an active metal. Said active metal which is for example at least one element of the group Hf, Ti, Zr, Nb, or Ce, produces a connection between the solder and the ceramic via chemical reaction, while the connection between the solder and the metal is a metal hard solder connection.
In the solder process, the active element forms a reaction layer with the ceramic, which can be sprinkled by the other solder elements during the solder process. Usually, active solders are applied and to the connection partners on the spots where the connection shall be provided, as a paste in which the active element is provided as particles, by serigraphy.
The geometry of the reaction layer, however, resulting from this, entails substrates/composite materials, which are not ideal with respect to their thermal and mechanical properties. Moreover, the method is relatively costly due to its important silver consumption.
Furthermore, the use of rolled solder belts having an active solder composition is also known in the art, but these are not appropriate, either, to remedy the aforementioned disadvantages, as, here, an ideal formation of the reaction layer is not possible, either.